noun
Christmas blues; holiday stress in December
Refers to the stress, fatigue, or low mood many people feel during the busy December holiday season, often due to year-end work, social obligations, and financial pressure.
１２月病で、忘年会に行く気がしない。
I have the Christmas blues and don't feel like going to the year-end party.
１２月病にならないように、早めに仕事を片付けよう。
Let's finish work early so we don't get holiday stress in December.
五月病 refers to a similar low mood or lack of motivation that often hits new students or employees in May after Golden Week, while １２月病 is specifically tied to the December holiday season.
Compound of １２月 (December) and 病 (illness), modeled after 五月病 (May blues). The term describes a seasonal low mood rather than a medical condition.